US2606084A - Spindle bearing for surveying instruments - Google Patents

Description

Aug. 5, 1952 H. R. LARSEN ET AL I SPINDLE BEARING FOR SURVEYING INSTRUMENTS Original Filed May 5, 194'? Y. Bnfientors Harold R..Laxsen 8. Daniel Gurney (Ittornegs Patented Aug. 5, 1952 UNITED STATES PATENT ()FFICE 2,606,084' SYPINDLEBEARING FOR-SURVEYING, r I

INSTRUMENTS Harold R. Larsen, Troy, and -Daniel Gurney,

- Jamestown, N. Y., assignors to W. & L. E. Gurley", Troy, N. Y., a corporation of New York Original application May 5, 1947, Serial No.

745,930, now Patent No. 2,570,568, dated Octoher 9, 1951. Divided and this application July 27, 1950, Serial No. 176,232

This invention relates to surveying instruments and particularly. to the soecalled spindle bearing whichjdefines the vertical geometrical axis of the instrument. 7

The present applicationis a division of our apphcation Serial No '745,930,1 now: Patent No. 2,570,568, and. the benefit of the filing date of that application, May 5, 1947., is claimed. Since the problem is .to produce a precise bearing on which the telescope turns, it is simpler to explain the invention as embodied in a level. The invention can, however, be used in connection with more, complicated instruments, such as transits and theodolites. .The added complication in connection with instruments of the types just mentioned arises from the presence of a secondand coaxial bearing which supports the horizontal limb. Since that second bearing is not involved in the present invention, nothing is sacrificed by disclosing the invention as used in alevel.v

According to the present embodiment of the invention both bearings are ofthe preloaded, cylindrical-race type. Within narrow limits 2. bearing so constructed is indifferent to misalignment. A thrust bearing. is required and takes a simple form which is practically friction-free.

From a manufacturing standpoint, the problem in producing a precise spindle bearing of the ball type involves the production of truly coaxial races at the top and bottom of the spindle and at the top and bottom of the bearing sleeve. As will be explained fully hereinafter, the commercial importance of the present invention resides in the design of the races so that they can be made truly coaxial by simple manufacturing processes. The importance of these considerations is reflected in the fact that no adjustment is needed. Precision turns solely on accuracy of manufacture, and is limited only by the precision with which bearing balls can be produced.

The invention will now be described by reference to the accompanying drawing in which the single figure is a view, chiefly in vertical axial section, through a leveling head constructed according to the invention.

The usual base plate is indicated at B. This plate is intended to be mounted on a tripod not shown in the drawing. The base 8 has the usual central aperture with a'bushing 1, affording the usual concave spherical bearing seat for the spherical head 8. This is formed on a nut 9. Th nut 9 is threaded at H upon the tubular bearing sleeve l2. The threads ll engage the sleeve l2 in an area above the lower end of the 2 Claims. (c1. cos-174) sleeve and above thelower internal bearing race hereinafter described. Sleeve l2 has at its upper end an external enlargement l3 which surrounds the upper bearing race and affords an external shoulder I4 some distance below this race. .A spacing sleeve I5 surrounds the sleeve 12 and engages the shoulder l4. The sleeve I5 engages the top of the cruciform leveling head l6 while the nut 9 engages the lower side thereof. In this way the bearing sleeve l2, the sleeve l5 and the leveling head I6 are locked together by the nut 9 and so form a unitary structure. The stress exerted by the nut is so localized that there is no tendency to deform the sleeve l2. On the contrary, the sleeve is simply stressed in tension. Pursuant to this same idea, the sleeve l5 has at its top a cylindrical extension ll,.which.is spaced from the head I3 on the sleeve [2 and is shouldered to. receiveand support the clamp l8, forming apart of a tangent screw mechanism, notillustrated in detail. The significant. aspect of the construction is that the clamp-I8. may be engaged and releas'edwithout devolopingdistorting. stresses in the bearingsleeve l2. This follows from the fact that the clamp engages only the sleeve'l5 and only that portion .ofthat sleeve which is spaced from the sleeve. The arms of the leveling head It are provided with the usual leveling screwslfi', each of said screws having a universally mounted thrust head 2| which engages the upper surface of the base plate 6.

The lower end of the nut 9, i. e. the end below the spherical head 8, is closed by a screw plug 22. The sleeve [2 has a straight cylindrical bore 24 which is highly precise and is produced by grinding, lapping and honing to th desired finished diameter. A spindle 25 below the flange 21 is a precisely formed true cylinder of uniform diameter except for the retaining groove hereinafter described. The spindle 25 is attached by means of threads 34 to the frame of the level.

The bore of sleeve 12 serves as the outer race for balls mounted between it and the spindle 25 under preload. The upper balls 28 are spaced by an apertured retainer 35. The lower series of balls 3| are spaced by an apertured retainer 32. A ball 36 mounted in a socket formed in the lower end of the spindle 25 at the axis of the spindle serves as a thrust bearing and engages the plug 31 which is screwed into the lower open end of the sleeve [2. To maintain the parts in assembled relation a screw 38 is threaded into the sleeve l2 and carries at its end a stem which enters a groove 39 encircling the spindle 25.

ment of the invention but which areindicative of the degree of preloading desired and the dimensions used to secure it. In that example, the

outer race is ground, lapped and honed to a diameter of 03501310000025. The inner race is similarly precisely finished to a diameter of 0.4378:0.000025. The diameter of the balls is 0.15625:0.000011. I under a compression amounting to 0.0001. This strain is well within the elastic limit of the ball We claim:

1. A vertical spindle bearing structure for use in surveying instruments comprising in combination a rotatable vertical cylindrical spindle; a normally fixed encircling coaxial sleeve having a cylindrical bore; two longitudinally spaced bearings interposed each between the spindle and the sleeve, each bearing comprising a single circular series of balls encircling the spindle and confined between the cylindrical surfaces of the spindle and of the bore of the sleeve, the balls being so dimensioned relatively to the spindle and sleeve Consequently theballs are and assures precise support of the spindle withr in the bearing sleeve. It would be possible to preload-the balls even more highly but the suggested preloa'ding is sufficient;

It is important to observe that a preloaded ball bearing having two cylindrical races is practicallyindifi'erent to alignment within a minute angular displacement of the spindle which could be caused by inaccuracies of manufacture. Misalignment'has the effect of converting thev ball pat-h from a circle to an ellipse but if the angle of misalignment is small and it cannot be large in this case, the difierence between the major and minoraxes of the ellipse is infinitesimal and much less than the degree of preloading. As a consequence it can have no material effect. Thus, the construction shown in the present application is indifferent tomisalignmen't of that degree which could possibly.o'ccur in-commercial .practice.

Anotherimportant feature of the device is'the fact'that the outer sleeve I2 is stressed only in tension developed strictlyiin' the'direction of its geometrical axis; which of course is an axis of symmetry. Also the ends of sleeve l2 project beyond'the' engagement of nut 9 and the. plane of engagement of shoulder l4,.and the. bearingraces are located'in these projectingportions. As a consequence any tendency: toward distortion of sleeve-l2 is minimized. Furthermore, the races are located in portions of the sleeve substantially unaffected by. such distortion asmight conceivably occur. 4

that the balls are confined under a degree of loading less than the elastic limit of the balls; retainer means serving to space said balls in two circular series; and a thrust bearing arranged to react on saidspindle, at and in the direction of its axis.

2. A vertical spindle bearing structure for use in surveying instruments comprising in combination a rotatable-vertical cylindrical spindle; a normally fixed encircling coaxial sleevehavin'g a cylindrical bore; ltWO longitudinally spacedbearings interposed each between the spindle andthe sleeve, each bearing comprising a circularcserles of balls encirclingthe spindle andconfined between the'cylindrical surfaces of the spindle and of the bore of the sleeve, the balls beingso dimensioned relatively to-the spindle and sleeve that the balls are confined under a degree or loading less than the elastic limit .of the balls; retainer means servinglto space said balls in twotclrcular series; a thrust bearing arranged to react on said spindle, at andin the direction of its axis; I and supportingmeans arranged to engage said sleeve and stress it axially in tension between planes each of which is spaced from and located begwizen the planes of the two circular series of a ls.

.' HAROLD R. DANIEL GURNEY.

REFERENCES CITED V FOREIGN PATENTS Country Date a Great Britain July 23, 1925 Number

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